From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48621C433E8 for ; Thu, 23 Jul 2020 14:26:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 25ED420771 for ; Thu, 23 Jul 2020 14:26:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="PMLkNsZx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729411AbgGWO0g (ORCPT ); Thu, 23 Jul 2020 10:26:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48840 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726089AbgGWO0g (ORCPT ); Thu, 23 Jul 2020 10:26:36 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3F2D3C0619DC; Thu, 23 Jul 2020 07:26:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=wwAZ4+QkYVfMEHOVd3BXrZYoQyQVya/EkyI6lTMJuEc=; b=PMLkNsZxkfipkQdx59Ts5gbSgy ODJbDs/oG8tcz8/eohMUTIz+JBG8PYDPFQKWJMwDegGQl83DK2H4STe5I0pz7ZqX8KdZzt/EiC9Os dzdb+OE63JAGbPDhIco+b5j1Yy3qEnFWRiNqz1O3tImnIJ3Pkcar23kbnxKbQKOS+OPuXYKMniIGR pP5J4QQFMcVKpENacLV0k/slNjU1uyWx4kIShROCXfnBpF6JKLJ+mScEmbPN9YtO6oDhGnSmeAuVr 91tN4f4u0hpzoB0inLOFLV0Na6vJeadwIpqLOlss8qCFFij3lla63yca6jWqOzYWlPEGrdBDYYnlN rQouaYzw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jycAz-0006IN-CG; Thu, 23 Jul 2020 14:26:25 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 5BE1A983422; Thu, 23 Jul 2020 16:26:23 +0200 (CEST) Date: Thu, 23 Jul 2020 16:26:23 +0200 From: Peter Zijlstra To: Thomas Gleixner Cc: Alex Belits , "frederic@kernel.org" , "rostedt@goodmis.org" , Prasun Kapoor , "mingo@kernel.org" , "davem@davemloft.net" , "linux-api@vger.kernel.org" , "linux-arch@vger.kernel.org" , "catalin.marinas@arm.com" , "will@kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" Subject: Re: [PATCH v4 00/13] "Task_isolation" mode Message-ID: <20200723142623.GS5523@worktop.programming.kicks-ass.net> References: <04be044c1bcd76b7438b7563edc35383417f12c8.camel@marvell.com> <87imeextf3.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87imeextf3.fsf@nanos.tec.linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Thu, Jul 23, 2020 at 03:17:04PM +0200, Thomas Gleixner wrote: > 2) Instruction synchronization > > Trying to do instruction synchronization delayed is a clear recipe > for hard to diagnose failures. Just because it blew not up in your > face does not make it correct in any way. It's broken by design and > violates _all_ rules of safe instruction patching and introduces a > complete trainwreck in x86 NMI processing. > > If you really think that this is correct, then please have at least > the courtesy to come up with a detailed and precise argumentation > why this is a valid approach. > > While writing that up you surely will find out why it is not. So delaying the sync_core() IPIs for kernel text patching _might_ be possible, but it very much wants to be a separate patchset and not something hidden inside a 'gem' like this.